In typical induction heating systems, accurate and close control of the operating temperature of the workload is generally required. Moreover, it may become necessary for various sections of the workload to require different levels of heating such that each section of the workload must be closely controlled for accuracy.
For example, Simcock, U.S. Pat. No. 5,059,762, discloses a multi-zone induction heating system which includes a plurality of inductive coil sections. Each of the inductive coil sections is associated with a respective zone of the work load. Power from a supply is applied to each one of the coil sections through a respective one of a plurality of saturable reactors. Each one of the saturable reactors is operable to shunt a proportion of supply power to its respective inductive coil section in response to a demand signal derived from the operation of the respective zone for such induction coil section. Accordingly, the temperature in each zone is regulated independently of the regulation of the other zones.
Increased precision in the temperature regulation of the work load may necessitate that the regulated zones become smaller. Smaller zones may further necessitate smaller zone spacing between inductive coil sections, thereby bringing the work coil in each section closer the work coil in neighboring sections. Since a high frequency current is applied to each work coil to develop the inductive field used to heat the work load, such field developed by one work coil may in part pass through the core of a neighboring work coil causing magnetic interference or energy transfer between coils, thereby resulting in crosstalk between coils.
It is readily seen that crosstalk may then become more severe as the work coils are brought closer together. As crosstalk increases, the reliability of the each of the power modules driving each respective one of the work coils is significantly reduced. Accordingly, a need exists to reduce crosstalk in a multi-zone induction heating system in order to provide greater reliability for the power modules.